The present invention provides a fluorescent substance composite glass which is chemically stable, has a large size, is reduced in wall thickness, has a uniform thickness and therefore has a high energy conversion efficiency; a fluorescent substance composite glass green sheet and a process for producing the fluorescent substance composite glass. The fluorescent substance composite glass of the present invention is produced by baking a mixture containing a glass powder and an inorganic fluorescent substance powder, in which the energy conversion efficiency to a visible light wavelength region of 380 to 780 nm is 10% or more, when light having an emission peak in a wavelength range of 350 to 500 nm is applied.